From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, HTML_MESSAGE,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 825E4C4361B for ; Tue, 15 Dec 2020 11:42:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EA1C422285 for ; Tue, 15 Dec 2020 11:42:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA1C422285 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 073766B0036; Tue, 15 Dec 2020 06:42:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id F3F1E6B005D; Tue, 15 Dec 2020 06:42:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E061F6B0068; Tue, 15 Dec 2020 06:42:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0068.hostedemail.com [216.40.44.68]) by kanga.kvack.org (Postfix) with ESMTP id C7AD46B0036 for ; Tue, 15 Dec 2020 06:42:47 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 7D613362A for ; Tue, 15 Dec 2020 11:42:47 +0000 (UTC) X-FDA: 77595329574.20.knot30_500d91f27423 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 62018180C07A3 for ; Tue, 15 Dec 2020 11:42:47 +0000 (UTC) X-HE-Tag: knot30_500d91f27423 X-Filterd-Recvd-Size: 6318 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Dec 2020 11:42:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608032566; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to; bh=VyTF8bOewsx1oLAH+doIITYQeEkOmKkn3LY/Qz8BcTU=; b=J9gUwvVO4CoGp7ISlqCBv3qRstDiA/lPu4tZICxl8sNVJ8P1dWTr7VdAT0+qKJHd/D+wFs J+g/xOOB+kFxDHKAgeF9DGbJRGxtnLRBCxXvPO0bNCjQadLcHUgJS4BHGMbJIEBPwyfinK XgetWLX0ggflzfzSao5NAQLvzXpH6Ec= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-121-Wcwmr4kYNMaxQTsB2VRMIg-1; Tue, 15 Dec 2020 06:42:42 -0500 X-MC-Unique: Wcwmr4kYNMaxQTsB2VRMIg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C193818C8C01; Tue, 15 Dec 2020 11:42:40 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A1FD219C44; Tue, 15 Dec 2020 11:42:40 +0000 (UTC) Received: from zmail23.collab.prod.int.phx2.redhat.com (zmail23.collab.prod.int.phx2.redhat.com [10.5.83.28]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 67B9C18095C7; Tue, 15 Dec 2020 11:42:40 +0000 (UTC) Date: Tue, 15 Dec 2020 06:42:39 -0500 (EST) From: Chunyu Hu Reply-To: Chunyu Hu To: linux-mm@kvack.org Cc: hannes@cmpxchg.org, guro@fb.com, akpm@linux-foundation.org Message-ID: <1273738630.62467759.1608032559889.JavaMail.zimbra@redhat.com> In-Reply-To: <223826327.62466770.1608031937021.JavaMail.zimbra@redhat.com> Subject: Question about admin_reserve_kbytes in GUESS mode MIME-Version: 1.0 X-Originating-IP: [10.72.12.72, 10.4.195.20] Thread-Topic: Question about admin_reserve_kbytes in GUESS mode Thread-Index: /z5ntpZ7LanKjxxurh8RgA/bOu5ubA== X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=chuhu@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/alternative; boundary="----=_Part_62467758_1087297679.1608032559887" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: ------=_Part_62467758_1087297679.1608032559887 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Hello experts, I find admin_reserve_kbytes is not working as documented since commit 8c7829b04c523cdc(mm: fix false-positive OVERCOMMIT_GUESS failures). Before that, available free pages are used to determine the allocation check, and admin_reserve_kbytes was honored in the default GUESS over_commit mode. While after that commit, admin_reserve_kbytes is not honored in default mode any more. This looks like break the sysctl usage? Documentation/admin-guide/sysctl/vm.rst: admin_reserve_kbytes ==================== The amount of free memory in the system that should be reserved for users with the capability cap_sys_admin. admin_reserve_kbytes defaults to min(3% of free pages, 8MB) That should provide enough for the admin to log in and kill a process, if necessary, under the default overcommit 'guess' mode. ....... -- Regards, Chunyu Hu ------=_Part_62467758_1087297679.1608032559887 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Hello experts,
I find admin_reserve_kbytes is not working as documented since =
commit 8c7829b04c523cdc(mm: fix false-positive OVERCOMMIT_GUESS = failures).

Before that, available free pages = are used to determine the allocation check,  and admin_reserve_kbytes<= br>
was honored in the default GUESS over_commit mode. While afte= r that commit, admin_reserve_kbytes
is not honored in default= mode any more. This looks like break the sysctl usage?

<= /div>
Documentation/admin-guide/sysctl/vm.rst:

admin_reserve_kbytes
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D

The amount of free memory in the system that= should be reserved for users
with the capability cap_sys_admin.
&nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;         
admin_reserve_kby= tes defaults to min(3% of free pages, 8MB)

That should pr= ovide enough for the admin to log in and kill a process,
if necessary, u= nder the default overcommit 'guess' mode.

....= ...


--
Regards,
Chunyu Hu

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